Abstract 2958: ONC206, an imipridone derivative, induces cell death through activation of the integrated stress response in serous endometrial cancer in vitro

Abstract Objectives: ONC206 (Oncoceutics) is a selective dopamine receptor D2 (DRD2) antagonist and an analogue of ONC201, an imipiridone currently being investigated in phase II clinical trials for serous endometrial cancer (EC). ONC206 has been shown to inhibit cell proliferation through activation of the integrated stress response (ISR) and apoptosis in brain, breast, and colorectal cancer cell lines. Thus, we investigated the efficacy of ONC206 for serous EC as well as its underlying mechanism of action. Methods: The serous EC cell lines, ARK1 and SPEC-2, were used. Cellular proliferation was measured using MTT assay. Cleaved caspase-3 and 9, markers of apoptosis, were assessed by ELISA assays. Adhesion and invasion were assessed by laminin and wound healing assays, respectively. Relative In vitro ISR was estimated by ROS and JC-1 assays. Western immunoblotting evaluated effects of ONC206 on proteins central to cellular stress and invasion. All statistical analyses were performed using the software Prism 8 (GraphPad). Results: ONC206 inhibited cellular proliferation in a dose-dependent manner and was more potent than ONC201 in ARK1 (IC50=0.33uM vs IC50=1.59uM) and SPEC-2 (IC50=0.24uM vs IC50=0.81uM) cell lines. Treatment with ONC206 decreased JC-1 fluorescence (p=0.001-0.01), and increased ROS production (p<0.001), cleaved caspase-3 (p=0.008-0.02), and caspase-9 (p=0.02-0.04) activity in both cell lines. ONC206 increased expression of the stress proteins ATF4, PERK, and BiP. Adhesion (p=0.01-0.02) and wound healing (p<0.001) were significantly impaired after treatment with ONC206 and was accompanied by decreases in proteins Slug, Snail, Vimentin, and VEGF-C. Pretreatment with stress inhibitor n-acetylcysteine (NAC) significantly attenuated the efficacy of ONC206 on ROS production (p=0.001-0.01), wound healing (p<0.001), and proliferation (p=0.001-0.002) in both cell lines. Conclusions: Our results suggest that ONC206 demonstrates nanomolar potency for the inhibition of proliferation in serous EC cell lines. Specifically, ONC206 utilizes ISR activation as a significant pathway in the propagation of its anti-proliferative and anti-metastatic effects. Thus, ONC206 may be a promising agent in serous EC which has limited treatment options. Citation Format: Yingao Zhang, Yu Huang, Yajie Yin, Yali Fan, Katherine Tucker, Allison Staley, Varun Prabhu, Joshua Allen, Chunxiao Zhou, Victoria Bae-Jump. ONC206, an imipridone derivative, induces cell death through activation of the integrated stress response in serous endometrial cancer in vitro [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 2958.